(1) Field of the Invention
The invention relates to a coil wire for suppressing electromagnetic interference, and more particularly to a wiring design which can protect a cable from electromagnetic interference (EMI).
(2) Description of the Prior Art
Recently, innovation upon the communication technology has been expediting the development of computer peripherals such as monitors and the like displays. For a display, no matter it is a thin film transistor liquid crystal display (TFT-LCD), a plasma display panel (PDP) or a liquid crystal display (LCD) of other types, rapid data transmission through cabling is the trend to achieve high-quality visions. However, under such an application, electromagnetic interference (EMI) has become a more and more severe problem. For the low-frequency electromagnetic interference with frequencies lower than 500 MHz, it is well known to suppress the electromagnetic interference of a cable by introducing a ferrite core. Yet, such a design can still fail to waive the cable from high-frequency noises. It is noted that the electromagnetic interference can not only happen to the cable for connecting the liquid crystal display and the computer host. Similar problems also happen to power cables and other cable lines that connect computer peripherals to the computer host. For usage of the rapid data transmissions the ferrite core is usually used to wrap the power cable or the cable line at one end to reduce the effect of the electromagnetic noises.
Currently, for cable lines in the market, especially for the LCD cables, most of the cable lines utilize the ferrite cores to enhance their resistance against the electromagnetic interference. Nevertheless, the performance of the ferrite core on suppressing the electromagnetic interference is mainly dependent upon its material property, inner diameter, outer diameter, length and so on. Generally speaking, the ferrite core can be useful to suppress a noise with a frequency lower than 500 MHz. On the other hand, for a noise with a frequency larger than 500 MHz, the ferrite core may fail to suppress the electromagnetic interference. Further, the ferrite core may strengthen its resistance against the electromagnetic interference by increasing its inner diameter or its length. Yet, upon such a change, the trade-off would be the appearance, the volume, the weight and the cost of the cable, while the strengthening of the resistance might still be limited. Actually, in the art, no complete resolution can be provided to suppress the electromagnetic interference.
On the other hand, as a standpoint of computer manufacturers, it is much economic and good-looking to construct most of related power cables onto a mother board of a computer. For example, if a 12V DC source for an LCD monitor of a personal computer (PC) can be constructed directly onto a mother board of the computer, additional external power adapter is then no more required so that more convenience and a cost-down can be provided to the computer system. But for the dark side, the electromagnetic interference may be easily arisen by locating the 12V DC source such close to another source for a decoder IC of the LCD monitor.
In an ordinary design of an LCD PC, an LCD cable for the monitor is mainly divided into a part for data transmission and another part for forming a 12V DC power cable. The part for data transmission is usually shielded by a braided wire. The part for forming the 12V DC power cable is usually grounded through a thin wire. As shown in FIG. 1, the connecting cable 1 in the art mainly includes two terminal connectors 7 and 8 for bridging a peripheral device (an LCD panel for example) and the computer host. The connecting cable 1 comprises a middle splitter 3 for bifurcating the connecting cable 1 into a power cable 4 and a signal line 5. The power cable 4, used to provide electricity to the peripheral device, has a free end formed as a DC plug 9. The signal line 5 is the part of the connecting cable 1 that is used for data transmission. As shown, one end of the signal line 5 is the terminal connector 8 for engaging with the peripheral device, and the other end thereof is connected with the power cable 4 at the splitter 3. The terminal connector 7 of the connecting cable 1 opposing to the splitter 3 is prepared to engage with the computer host. In this design, the signal line 5 is a high-frequency signal line wrapped by a braided wire 6 to protect the electromagnetic interference.
To avoid the electromagnetic interference, the conventional connecting cable 1 as shown in FIG. 1 comprises a ferrite core 2 as an exterior shield for protecting the connecting cable 1 from the electromagnetic interference. However, several disadvantages of using the ferrite core 2 can be seen. As mentioned, upon using the ferrite core 2, many factors as the appearance, the volume, the weight and the cost can be at the weak side. Such disadvantages can be easily observed from FIG. 2, a perspective view of part of the connecting cable 1 of FIG. 1.
Hence, it is the motivation of the present invention how a connecting cable can be designed, by which the connecting cable can protect the power cable and the signal line from the electromagnetic interference, cost thereof can be kept within a reasonable range, and wiring thereof can provide a better appearance.
To overcome the aforesaid disadvantages of the prior art, the present invention firstly analyzes the product in FIG. 1 as a base line for further improvement. After carefully analyzing, it is found that both the braided wire for shielding the rapid data line (i.e., the high-frequency signal line) and the power cable can be interfered simultaneously by the high-frequency noise so as to render the problem of electromagnetic interference. In particular, the power cable is most interfered, for the connected ground wire of the power cable is usually too thin to provide adequate resistance for shielding. Fortunately, the power cable extends close to the braided wire after it leaves the LCD panel; so that a ground loop can be introduced to compensate the problem caused by the thin ground wire. However, in the practice, for plugging the power cable at a position close to the computer host end, the power cable needs to be arranged away from the braided signal line. Under such an arrangement, the ground wire is removed and the electromagnetic interference problem arises.
Therefore, the present invention introduces a novel structure in which the power cable is led to wrap the signal line with the braided wire. By providing rapid noise variation of the braided wire to go through the coil formed by the wrapping power line, a rapid change of magnetic flux can be induced to generate a reverse induced current for further eliminating the noise intensity on the power cable. Thereby, the electromagnetic interference problem can be reduced to a minimum, even if the power cable is away from the braided wire.
Preferably, in the aforesaid coil wiring of the present invention, a splitter can be included to fix the coil onto the signal line at the portion where the power cable wraps the signal line.
Preferably, in the aforesaid coil wiring of the present invention, a conductive cloth can be included to adhere the uncoiled power cable onto the signal line.
Preferably, the signal line with the braided wire can be a high-frequency signal line, and the power cable can be a DC power cable.
Preferably, the performance of reducing the electromagnetic interference on the connecting cable by providing the coil wire of the power cable is dependent substantially upon the coil number of the wiring. Also, by provided with adequate coil number of the wiring to the power cable, the high-frequency noise with the frequency higher than 500 MHz can be effectively suppressed.
Preferably, in the coil wiring of the present invention, a pattern of regular wiring can be introduced to wrap the power cable around the line.
All these objects are achieved by the coil wire for suppressing electromagnetic interference described below.